COVID-19(7) Patient(5) Analysis(5) median(5) vasoconstriction(3) Retrospective study(3) Macroaggregated albumin(3) Mild(3) healthy(3) explained(3) patients(3) Embolism(3) pulmonary thrombosis(3) average(3) patient cohort(3) lung(3) evaluate(3) applied(3) incidence(3) parenchymal(3) association(3) Lung perfusion abnormalities(3) median age(3) abnormality(3) thrombosis(3) male(3) performed(3) CT scans(3) the patient(3) semi-quantitative(3)